Method of Incrementally Reducing and Stretch Straightening Shaped Metal Components

ABSTRACT

A drawing unit with a segment reciprocating die for drawing metal segments comprises a tensioning device arranged to advance a shaped specimen through an array of dies that create a shaped orifice with the spacing formed between the dies. These dies segments act under the influence of a powered unit to move in a reciprocating motion that causes the spacings between segments to increase and decrease synchronously thereby shaping the metal segments.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 16/687,168, filed Nov. 18, 2019, which is hereby incorporated hereinby reference.

BACKGROUND OF THE INVENTION Field of the Invention

This invention is directed to a method for shaping a metal component bycyclically striking the component with multiple reciprocating contactdies as the component is moved along a longitudinal axis relative to thedies.

Background of the Invention

The drawing of shaped specimens involves a die with a specificallyshaped inlet and a pulling mechanism to advance, or “draw”, the shapedcomponent through the die in order to force a cross sectional reductionof the shape. Significant levels of surface sliding occur under thecompressive loading condition which occurs while in contact with thereducing die. The presence of frictional forces at this interface hastwo dominating negative implications. The first implication of frictionis that it increases tension required for a given reduction and lowersthe maximum reduction possible before tensile tearing or necking of thereduced portion of the specimen occurs. The second negative implicationis that friction increases the occurrence of sliding defects on thesurfaces, such as galling, tearing, or striations. As a result, thesuccess of traditional drawing in delivering adequate “per pass”reductions and acceptable surface quality is tied to maintaining a lowcoefficient of friction between the die and the specimen.

Maintaining a low coefficient of friction is not always easy orpossible, particularly when reducing pieces at elevated temperatures.The most common lubricants in drawing are oil or grease based, whichhave low thermal stability. Solid film type lubricants such as graphitealso thermally degrade below the common hot working temperatures of manymetals. As a result, effective lubricants are insufficient to enableeffective drawing for many alloys that require deformation to occur athigher temperatures.

In U.S. Pat. No. 2,393,131 a lower observed friction coefficient indrawing is achieved by applying vibration to an otherwise static diegeometry. In this, the orifice geometry is constant and fixed, and theentire die exhibits a small vibration. Contrastingly, in U.S. Pat. No.3,585,832 regarding drawing, a cyclic tensile load was applied by thepulling mechanism to pull a specimen through a static die in order tolower the average tensile force required in drawing. Though both priorarts focus on lowering effective contact friction, the underlyingsliding mechanics in the die remain in governance of the draw forces ofthe drawing process. As a result, difficulties in drawing materials athigh temperatures with standard drawing will largely remain congruent,perhaps with marginal improvements from lower friction coefficients.

In U.S. Pat. No. 3,575,029 a roller-based reduction method resulting inhigher reduction per pass of the specimen in comparison to simplyrotating rollers is achieved by coupling rollers to series of linkagesthat results in a walking motion when driven by eccentric drives. Thisconcentrates the contact pressures into a small area relative to thespecimen transition zone as compared to a simply rotating roller. As aresult, the total compressive forces within a given instant are lowerand potential specimen per-pass reduction is higher. The shortcoming ofthe use of this device lies in the complexity and technical difficultyin building long lived rotating and sliding joints exposed to hightemperatures for long periods. Operating rotating rollers at or near thetemperature desired for difficult to work materials would requirecomplex cooling or expensive connections to achieve operationalreliability.

In U.S. Pat. No. 3,727,443 a series of ring—shaped arrays of sphericalroller bearings were substituted for a static die to draw and reduce thecross-sectional area of tubes. The rings of spheres were rotated atgiven speeds while the part advanced through the contact area, while astatic mandrel maintained the inner diameter sizing, thus impartinghelical reduction of the exterior surface of the tube. Through controlof speed and placement of the path of the helical contacts, with twosets of rollers of differing in number, complete reduction of the tubewas achievable. While this was effective at lowering friction and inachieving an improved surface finish, the invention is only applicableto the deformation of tube structures. Additionally, the reduction wasapplied to portions of the cross section at a given time creatingdifferential deformation through the reduction zone. Differentialreduction can result in loss of straightness, residual stress, or evenstrain related microstructure defects in some materials such as shearbanding.

Departing from inventions relating to drawbench design, the occurrenceof reciprocating dies or hammers to reduce and reshape metal can befound in U.S. Pat. Nos. 391,825, 455,905, 1,180,296, and 2,114,302. Allembodiments involved a radial arrangement of reciprocating dies toreduce or re-shape bar and simple shaped specimens. In U.S. Pat. No.391,825 four radially arranged dies reshaped the end of a round bar. InU.S. Pat. No. 455,905 six alternating radially arranged dies withcontact overlap were employed for reducing round material. In U.S. Pat.No. 1,180,296 several sets of radially arranged dies were placed insequence to impart multiple reductions per pass of a bar or ingot. InU.S. Pat. No. 2,114,302 a radial arrangement of reciprocating dies wasused specifically to reshape square metal bar into round metal bar. Inall reciprocating die prior arts, the dies are all radially arrangedwith a common center to only work round, tubular, or other simplegeometric shapes (i.e. squares, hexagons, octagons, etc.). This wouldnot enable the imparting of reduction to specimens having complex crosssections of varying geometries. Thus, the prior arts fail to deliver amethod to manufacture complex geometry specimen. Also, none of thesearts present the coupling of a maintained tensile force on the outgoingmaterial specimen for straightening and residual stress reduction.Failure to tension and/or stretch outgoing material forfeits the abilityto straighten or stress relieve through tensile yielding, which resultsin subsequent and costly straightening processes.

In U.S. Pat. Nos. 535,446, 773,197 2,178,141, 2,999,405, 3,645,126,3,728,890, and 4,229,963 reciprocating dies were also used inmetalworking, however the focus of these arts lies on the arrangementand means of actuation.

In U.S. Pat. No. 535,446 a flexible connection was used to mount thedies to the powering device to allow transfer of die inertia throughless constrained impact motions. The downside of this is that limitedcontrol exists on the stopping point of the dies. As such, specimenthickness control is diminished.

In U.S. Pat. No. 773,197 a force was imparted on floating dies by alobed shaft on the back face of the die. This die actuation mechanismallows a high rate of die impulses with lower shaft rotating speedthrough the back striking of the contact dies. Management of specimenadvance would be less consistent because die pieces have minimalposition constraint when not under the influence of contacting lobe.This would result in varying reduction bites and potential fordistortion in the specimen.

In U.S. Pat. No. 2,178,141 a series of radially arranged reciprocatingdies with very long contact down the length of a metal tube straightensthe material within the bite, or die clamping, while imparting a minimallevel of cold forming reduction on the cross section. The extendedlength of reduction bite aims to straighten by yielding the pipe whileconstrained in the straight condition. This straightening technique withan exaggerated contact zone would provide extended contact time with thedie material. Reducing the specimen cross section at elevatedtemperatures would lead to significant heating losses at the contactsurfaces and non-uniform strain accommodation.

In U.S. Pat. No. 2,999,405 radially arranged dies were mounted toinwardly sloping supports that imparted compression when the dies sliddown the support toward the shared intersection or convergence of alltravel axes (plural). A shared actuator allows a high degree of controland consistency of the die reciprocation advancement for shared centerarchitectures. However, this architecture does not allow flexibility toreduce intricate shapes, especially those requiring die reciprocationwithout a shared convergence point.

In U.S. Pat. No. 3,645,126 radially arranged dies were powered with aseries of closed oscillating hydraulic circuits for each die. In theoperation of the art at higher frequencies to boost productivity andminimize contact time, water hammering effect and friction heating ofthe fluid would degrade system performance. Additionally, thecompressibility of the working fluid would limit the ability to havehighly controlled die stop positions to deliver consistent thicknesses.

In U.S. Pat. No. 3,728,890 six radially arranged dies are physicallycoupled with flexible shafts for improved control and synchronizationcompared to prior pneumatic versions of 6 die bar reducers. The physicalcoupling of reciprocating dies is effective provided a fixed arrangementof reciprocating mechanisms are present, as is the case with this art'sradial arrangement of dies. This fixed radial arrangement limits thespecimen geometry to rounds with limited adaptability to othergeometries.

In U.S. Pat. No. 4,229,963 inward compressions of dies were accomplishedthrough a rotating support frame connected to the dies throughconnecting rods. This coupled advance design provides a coordinatedadvancement of the die tools in a radial arrangement. However, thisarchitecture prevents forging of complex geometry specimen due tonon-adaptive die motions.

An additional category of loosely related reducing machines exists whichare categorized as walking die reducing machines. Unlike drawing basedinventions where parts are drawn through a reducing die, in thiscategory, various mechanisms are employed to generate a walking motionof a die along the length of a metal segment. This motion combines thecompression and advancing action into a single motion. Patents for suchmechanisms include: U.S. Pat. Nos. 1,549,527, 2,153,839, 3,114,276,3,374,654, and 3,626,746. In U.S. Pat. Nos. 1,549,527, 2,153,839,3,114,276, and 3,374,654 varying combinations of eccentrics and linkagesare presented to generate compressive and axial translation motions ofthe contact dies onto the workpiece, heretofore called “walking motion”.In U.S. Pat. No. 3,626,746 one or more sliding wedge structures iscoupled with eccentrics and levers to generate similar walking motionsas other inventions with different mechanism architecture. In thesewalking motion prior arts, the combination of the compressive reductionaction with axial advance results in the advance without any advancingdevice. As a result, the ability to apply a tensile force to reducedportion of the workpiece in order to stretch straighten finished productis not provided. As such, any distortion imparted during reduction ofthe specimen will require additional post processing to remove.

BRIEF SUMMARY OF SOME OF THE PREFERRED EMBODIMENTS

The present invention involves a device for physically reducing thecross section of a shaped component into a finished or near finishedcondition. The current invention utilizes a series of die segments thatexhibit a synchronized reciprocation that imparts cross sectionalreduction on a specimen. The segment shape and arrangement create theorifice between the segments to match the specimen being reduced. Thearrangement and direction of reciprocation allows tailored opening andclosing of specific gaps or spacing to uniformly reduce various specimenfeatures in the reduction pass. The maintaining of tension on thematerial of the specimen that is exiting the die segments allowsoptimized tensile loading on the exiting material to yield the higheststraightness possible.

When reciprocation is less than the total reduction, the piece is neverfully out of the constraint of the die and the amount of specimenadvancement is limited before re-engagement is established within thedie. The case where reciprocation is more than the total reductioncontact is temporarily lost with each reciprocation and highlights thenext variant of embodiment.

When reciprocation is chosen to be larger than the total reduction or incases where higher levels of tension are sought, as in the case withbulky sections, two opposing tensioning devices are used on the end ofthe specimen entering and exiting the dies. The back tension isinsufficient to prevent the mechanism on the exiting material fromadvancing the specimen through the dies. In the variant wherereciprocation is larger than the total reduction, this provides themeans for maintaining constant tension on the specimen when die contactis lost during fully retracted states.

The decoupling of the magnitude of the tensile force from the amount ofreduction allows for much higher reductions to be imparted per reductionpass, and a specified tensile force to be applied to optimizestraightness and residual stress results in the reduced piece. Thisresults in improved straightness and the ability to reduce the number ofreduction passes required to yield the final, desired, specimencondition.

The present invention mechanism offers relatively high frequency andrelatively small reciprocation travel to deliver very refined andconcise final dimensions and surfaces. The high frequency offers hightravel velocity of the specimen through the die, low contact times withdies, and more contacts with a given point on the specimen. The highprecision of reciprocation travel of the eccentric mechanism and theelectromagnetic actuator allow high levels of control of the thicknessuniformity of the reduced specimen. The current invention deliversconsistent advancement and therefore reduction under the influence oftension. Precision is achieved with each die segment and coordinatedwith electronic control mechanisms. The current invention allowsindependent positioning or retracting of the die segments. This offersthe ability to adapt to varying shaped specimens as well as an open diearray to allow easier loading and unloading of specimen to startreduction.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of theinvention, reference will now be made to the accompanying drawings inwhich:

FIG. 1 is a top view of a draw bench constructed in accordance with anembodiment of the present invention depicting a grasping and pullingdevice on the specimen exiting a series of synchronized reciprocatingdies.

FIG. 2 is a cross sectional view of the drawn workpiece depicting thearrangement of synchronized reciprocating dies in the engaged positionaround a Tee-shaped product being one embodiment of the invention takenalong the sight lines A-A of FIG. 1 .

FIG. 3 is a cross sectional view of a reciprocating die mounted with anaxial sliding constraint, being one embodiment of the reciprocating diesin the current invention utilizing a powered eccentric to generate themotion, taken along sight lines B-B of FIG. 2 .

FIG. 4 is a schematic of an embodiment of the present invention showinga synchronized reciprocating die architecture to reduce a rectangularspecimen.

FIG. 5 is a schematic of another embodiment of the present inventionshowing a synchronized reciprocating die architecture to reduce tubularspecimen.

FIG. 6 is a schematic of another embodiment of the present inventionshowing a synchronized reciprocating die architecture to reduce roundbar specimen.

FIG. 7 is a cross sectional view of the die architecture for reducingtubes shown in FIG. 5 taken along sight lines C-C.

FIG. 8 is a schematic of an embodiment of the present invention showinga synchronized reciprocating die architecture to reduce a Tee-shapedspecimen with unconstrained shape extremities.

FIG. 9 is a schematic of an embodiment of the present invention showinga synchronized reciprocating die architecture to reduce a Tee-shapedspecimen with partially constrained shape extremities.

FIG. 10 is a schematic of an embodiment of the present invention showinga synchronized reciprocating die architecture to reduce an asymmetricand unequal thickness specimen of non-uniform thickness with varyingshape extremities.

FIG. 11 is a view of the die architecture, when the cam is at bottomdead center.

FIG. 12 is a view of the die architecture when the cam is at top deadcenter.

FIG. 13 is a view of the die architecture when the cam is in the nextcycle bottom dead center position.

FIG. 14 is a view of the die architecture when the cam is in the nextcycle top dead center position.

FIG. 15 is a cross sectional view of the drawn workpiece depicting thearrangement of synchronized reciprocating dies in the retracted positionaround a Tee-shaped product providing sufficient opening to enableuninhibited loading of said specimen prior to grasping, being oneembodiment of the invention taken along the sight lines A-A of FIG. 1 .

FIG. 16 is a cross sectional view of a reciprocating die, being oneembodiment of the reciprocating dies in the current invention generatingthe reciprocation motion via an electromagnetic actuator, taken alongsight lines B-B of FIG. 2 .

FIG. 17 is a view of the die architecture, at bottom dead center of thecam, to illustrate the method that the cycling actions, equal to orlarger than the total reduction, employs to reduce the Tee-shapedspecimen.

FIG. 18 is a view of the die architecture structure when the cam is attop dead center.

FIG. 19 is a view of the die architecture when the cam is in the nextcycle bottom dead center position.

FIG. 20 is a view of the die architecture when the cam is in the nextcycle top dead center position.

FIG. 21 is a top view of an embodiment of the present invention showinga grasping mechanism for clamping the part while imparting a tensileload to the workpiece generated by a pneumatic or hydraulic cylinder.

FIG. 22 is a side view of an embodiment of the invention shown in FIG.21 .

FIG. 23 is a top view is a top view of a draw bench constructed inaccordance with an embodiment of the present invention depicting agrasping and pulling device on the entry and exiting side of a specimentraveling through a series of synchronized reciprocating dies.

FIG. 24 is a top view of an embodiment of the present invention showinga grasping mechanism for clamping the part while imparting a tensileload to the workpiece generated by a linear actuator.

FIG. 25 is a side view of the embodiment shown in FIG. 24 .

FIG. 26 is a top view of an embodiment of the present invention showinga grasping mechanism for clamping the part while imparting a tensileload to the workpiece generated by a powered gear drive.

FIG. 27 is a side view of the embodiment shown in FIG. 26 .

FIG. 28 is a cross sectional view of a reciprocating die mounted on apivot to constrain the die to only a reciprocation around the mountingaxis, being one embodiment of the reciprocating dies in the currentinvention, taken along sight lines B-B of FIG. 2 .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The description of the device is intended for illustrative purposes andnot to limit the scope of the invention in any way. Referring first toFIG. 1 there is a machine for tensioning and advancing a shaped specimenthrough an arrangement of synchronized reciprocating contact dies toreduce the specimen's cross-sectional area. The machine includes apowered jaw 30, attached to a supporting frame to allow the applicationof a tensile load to the reducing specimen. A jaw on a travellingcarriage is the preferred and most common means used in draw benchapplications; however, any suitable means of applying tension to exitingmaterial after the reducing dies is compatible with the invention. Thespecimen, 32 is advanced under tension through an architecture of atleast one reciprocating contact die, modules 34, to impart reductioninto the specimen during the closing portion of the stroke and to allowaxial advancement during the retraction portion of the stroke. Inembodiments where two or more reciprocating dies are present, they willbe synchronized to compress and retract in unison. The reciprocatingdie(s) are mounted by a mounting member to transfer loading to theshared frame with the jaw carriage.

Referring to FIG. 2 , the arrangement of the reciprocating die modulesis shown to form the primary surfaces to reduce a Tee-shaped specimen32. The contact dies 36 are arranged to form the desired shape with thespacing between the contact faces of the dies. The dies can be made withvarying profiles of the contact face to facilitate varying convex, flat,or concave surfaces of shaped components. The axis of reciprocationtravel, upon which the die reciprocation 40 lies, is selected to providea desired reduction imparted into shape segments through the opening andclosing of the spacing between the die contact faces. The contact diesare mounted to a translating carriage driven by suitable means togenerate a reciprocating motion. In this embodiment an electric motor 42drives an eccentric shaft 44 inside of the module. In this embodimentthe motor rotation is synchronized electronically through a controlalgorithm. This embodiment also demonstrates a means of opening orretracing the entire module containing the reciprocation mechanism andmounting 34 in and out by means of a hydraulic cylinder 130 attached tothe module. The guiding and stop position of the modules when in theclosed or advanced position, as this figure illustrates, is constrainedby a slotted mount frame 132. During the reduction of specimen 32 thehydraulic cylinders 130 maintain sufficient force to ensure modules 34remain in contact with the hard stops on the slotted mount frames 132.

Referring to FIG. 3 . the die module in this embodiment generates axialreciprocation motion through the powered eccentric shaft 44, in order toreduce the Tee shaped specimen 32. A connecting rod 46 couples thereciprocating carriage 48 with the eccentric shaft. In the preferredembodiment the contact dies 36 are mounted directly to the reciprocatingcarriage. However, the use of intermediary mounting structures for loaddistribution, heat flow management, or other functional reasons may bedesired. The reciprocating carriage is constrained to axial travel bysliding journals 50 surrounding the sides of the carriage. The slidingjournals are mounted in a supporting frame 52 to which the eccentricshaft is also mounted. Coupled with this reciprocating die motion atensioning device 30 provides axial advance and tension force 54 to theTee-shaped specimen 32.

Referring to FIG. 4 in one embodiment a four radial die arranged inpairs 56 and 58 architecture can be used to reduce square or rectangularcross—sectional material 60 in the device. In some embodiments theamount of reduction in one directional pair 56 may impart differingstrain than in perpendicular directional pair 56. In some embodimentsone pair may have negligible lead in and reciprocation travel may beminimal merely to inhibit widening and allow unrestricted advancementvia tension through the retract portion of the die cycle.

Referring to FIG. 5 an embodiment of the invention is shown to allowreduction of tube structures 62. In this embodiment at least tworadially arranged dies with concave contact face contours 64 are presentto impart reduction of the outside surface of the tube structure. Asmall gap will be present between the contact OD outside diametercontact dies 66. In some embodiments this will form a small raised seamat this interface. In some embodiments the tensioning device impartsadequate rotation upon advance to allow subsequent die contact cycles tosmoothen the raised seam resulting from prior contact. In thisembodiment a sufficient flat land of the die would be present to fullysmooth any remnant of a raised seam in the material. A mandrel 68 issupported from the entry side of the drawing bench mechanism to provideform to establish the inside surfaces of the tube.

Referring to FIG. 6 an embodiment is shown reducing a round bar or wirespecimen 70 with three radially arranged synchronized reciprocating dies72. In some embodiments the specimen may be simply advanced through thereciprocating dies resulting in a raised seam that may need to beremoved. In the preferred embodiment a slight rotation around the axialline of travel would be coupled to each axial advancement of thespecimen following each reciprocation compression cycle. In thisembodiment there is a sufficient flat portion on the die extending pastthe reduction throat to provide a sufficient overlap to smooth theentire OD surface.

Referring to FIG. 7 the embodiment of the invention which enables thereduction of a tube-shaped specimen. In this embodiment tube specimen 62are loaded around a static mounted mandrel 68 on the entry side of thesynchronized reciprocating dies 64. On the exiting side of thereciprocating dies a powered jaw 74 is present to maintain the reducedsection of material under tension and advance the material forward 76.In the preferred embodiment the mandrel would have a forward taperingmandrel to allow free advancement of the piece without sliding on themandrel surface. In some embodiments the mandrel may be un-taperedprovided the friction between the tube and the mandrel is managed toprevent surface defects due to sliding. In all embodiments of thisinvention tensile forces on exiting material from a drawing action mustbe present to stretch straighten the component.

Referring to FIG. 8 the embodiment of the invention with the shown diearrangement is used to reduce a Tee-shaped specimen 78 withunconstrained extremities 80. In this embodiment the material at theextremity of the shape would have lower quality surfaces and may requiretrimming before use as a finished component. The need for endconstraints on the reciprocating dies 82 is governed by thepredictability and magnitude of widening or outflow of shapeextremities. This type of end constraint is considered within theconfines of the proposed invention for all conceivable shaped reductionarrangements.

Referring to FIG. 9 the embodiment of the invention with the shown diearrangement is used to reduce a Tee-shaped specimen with partiallyconstrained shape extremities 84. Partial constriction of die spacing 86beyond the shape on the reciprocating dies 88 allows the mitigation ofmaterial outflow—acting perpendicularly to the line of travel—of theextremities during reduction. This type of end constraint is alsoconsidered within the confines of the proposed invention for allconceivable shaped reduction arrangements.

Referring to FIG. 10 an embodiment of the invention is shown of anirregular shape 90 that demonstrates the versatility of the proposedinvention. In this architecture varying feature thicknesses exist acrossthe section. The current embodiment also demonstrates opening 92 andpartially closed end constraints 94 simultaneously on reciprocating die96 contact faces, as either is considered within the confines of theoutlined invention. This shape also demonstrates variation of placementof different features of the shape. In this embodiment the axis ofadvance 98 of the different synchronized reciprocating die segments donot share a common center or intersect. In a preferred embodiment theaxis of advance is selected to deliver comparable levels of strain invarying segments of a shape. In thicker segments 100, the stroke of thereciprocating dies should be proportionally larger than for thinnersegments 102 to impart comparable strains and prevent distortion.However, since the presence of a tensile force is present extant for allembodiments of this invention, a means of correcting any distortion ispresent through the tensile stretching of the specimen. As a result,equal strain in each segment is preferred but not required.

Referring to FIGS. 11, 12, 13, and 14 a time varying cross-sectionalview of the opposing die segments 104 reducing a leg of a Tee-shapedspecimen 78 is shown. In this embodiment axial tensile loading is placedon the exiting specimen with a tensioning device 30, possessing a meansfor grasping 1. In each time position the state of the eccentric crankshaft at bottom dead center 106 and top dead center 108 is shown toillustrate whether the die is in the compressed or the retracted stateof the reciprocation cycle. In the fully compressed state, a planedemarking the beginning 110 and end 112 of the zone of first deformationin the specimen is shown. In the retraction state shown in FIG. 12following a compression the specimen is allowed to advance a distance aportion of the way through the total previous bite—or die compressiononto the specimen—114. In the next compression cycle shown in FIG. 13the beginning 116 and end 118 of the second deformation zone is shown inrelation to the boundaries of the previous zone. In the subsequentretraction state shown in FIG. 14 the specimen and prior bites areallowed to advance a specified amount 120 to reposition within theupcoming bite region. The magnitudes of these axial advancements area afunction of the reciprocation die stroke 122 and the die lead ingeometry. Subsequently, the speed that a specimen will travel throughthe reciprocating reducing die will generally be in proportion to thefrequency of reciprocation assuming that the reciprocation stroke andgeometry remain constant. In the preferred embodiment each point alongthe length will be reduced under the influence of several overlappingreciprocation reductions. In this the preferred embodiments of theinvention the reciprocation travel or stoke 122 is less than half of thetotal reduction 124 of the specimen which provides inhibition ofunconstrained advancement of the specimen without the need for addeddevices to constrain advancement through the reciprocating die segments.

FIG. 15 depicts the same machine architecture as described in FIG. 2with the exception that the means for loading is demonstrated. Theretraction of the hydraulic cylinders 130 results in an opening ofreciprocating modules 34 and subsequent contact dies 36. This opening isto be sufficient to pass a segment of specimen through in order to beengaged by a grasping mechanism on the exit side of reciprocating diesin order to impart axial tensile force to straighten and advance thespecimen. Even in the retracted state the die segment modules 34 arestill under the constraining influence of the slotted mount frame 132.In this embodiment the reciprocation motion of the dies 36 would beactive as the hydraulic cylinders 130 advanced the module structure 34to the final stop position prior to drawing the specimen through thereciprocating die architecture.

Referring to FIG. 16 the die module in this embodiment generates axialreciprocation motion through an electromagnetic impulse generator 134,in order to reduce the Tee-shaped specimen 32. The impulse generator issecured to the module supporting frame 52. In the preferred embodimentthe contact dies 36 are mounted directly to the reciprocating carriage48. However, the use of intermediary mounting structures for loaddistribution, heat flow management, or other functional reasons may bedesired and are congruent within the scope of the present invention. Thereciprocating carriage is constrained to axial travel by slidingjournals 50 surrounding the sides of the carriage. The sliding journalsare mounted in a supporting frame 52 to which the eccentric shaft isalso mounted. Coupled with this reciprocating die motion a tensioningdevice 30 provides axial advance and tensile force 54 to the Tee-shapedspecimen 32.

Referring to FIGS. 17, 18, 19, and 20 a time varying cross-sectionalview of the opposing die segments 104 reducing a leg of a Tee-shapedspecimen 78 is shown. In this embodiment of the invention thereciprocation travel or stoke 122 is more than half of the totalreduction 124 of the specimen which would otherwise result in thecomplete disengagement and loss of the required tensile force resultingin the unconstrained advancement of the specimen. In this embodiment aprimary tensioning device 126 will be present on the exiting side of theapparatus. A secondary tensioning device 128 will be present on theentry side of the synchronized reciprocating dies to ensure that acontinuous tensile force is applied to the specimen and to meter therate of advancement of the specimen between the compressive strokes ofthe synchronized reciprocating die segments. In each time position thestate of the eccentric crank shaft at bottom dead center 106 and topdead center 108 is shown to illustrate whether the die is in thecompressed or retracted state. In the fully compressed state, a planedemarking the beginning 110 and end 112 of the zone of first deformationin the specimen is shown in FIG. 17 . In the retraction state followinga compression the specimen is allowed to advance a portion of the waythrough the total previous bite 136 as shown in FIG. 18 . In the nextcompression cycle shown in FIG. 19 the beginning 116 and end 118 of thesecond deformation zone is shown. In the subsequent retraction stateshown in FIG. 20 the specimen and prior bites are allowed to advance aspecified amount 136 to reposition within the upcoming bite region. Themagnitudes of these advancements are a function of reciprocation diestroke and die lead in geometry. It is desired that each point along thelength of a specimen will be reduced under the influence of severaloverlapping reciprocation reductions. In this embodiment the advancementper reciprocation and subsequently the velocity through thereciprocating dies is dictated by the conjoined travel of the primarytensioning device 126 and secondary tensioning device.

Referring to FIGS. 21 and 22 a top and side view of one of theembodiments of the tensioning device employed by the invention is shown.In this embodiment the specimen exiting the reciprocating reducing dies32 is partially inserted into the body of the grasping mechanism 138.Inside the grasping mechanism a cam style clamping mechanism 142 isrotated by a hydraulic cylinder 140 to compress all or portion of thespecimen in order to prevent the exit of the specimen. The graspingmechanism is powered by a double acting cylinder 144. In someembodiments the available cylinder 144 is actuated with pressurized air.In some embodiments the cylinder 144 is actuated with pressurizedhydraulic fluid.

Referring to FIG. 23 another embodiment of the invention is shown wherean exit tensioning device 126 and an entry back tensioning device 128maintain the specimen in tension and while advancing a shaped saidspecimen through an arrangement of synchronized reciprocating contactdies to reduce said specimen's the specimen cross-sectional area. Thisarchitecture of the invention is generally but not necessarilycorrelated with the die reciprocation depicted in FIG. 11 where the diescompletely disengage from the specimen at certain points ofreciprocation. The machine includes a primary tensioning specimen deviceon the exiting specimen 126 and a secondary—back tensioning—device onentering material 128 attached to a supporting frame to allow theapplication of a tensile load to be applied to the reducing specimen.The specimen 32 is advanced under tension through an architecture ofthree reciprocating contact die modules 34 to impart reduction into thespecimen during the closing portion of the stroke and to allow axialadvancement during the retraction portion of the stroke. In embodimentswhere two or more reciprocating dies are present, they will besynchronized to compress and retract in unison. The reciprocating die(s)are supported in an architecture to form a desired shape of the specimenduring reduction.

Referring to FIGS. 24 and 25 a top and side view of an embodiment of thetensioning device employed by the invention is shown. In this embodimentthe specimen exiting the reciprocating reducing dies 32 is partiallyinserted into the body of the grasping mechanism 138. Inside thegrasping mechanism a cam style clamping mechanism 142 is rotated by ahydraulic cylinder 140 to compress all or a portion of the specimen inorder to prevent the exiting of said specimen. The grasping mechanism inthis embodiment is powered by a mechanical belt driven linear actuator146. In some embodiments a dampening mechanism such as the depicted airspring 148 can be mounted between the grasping mechanism and thepowering device to provide a more continuous tensile load regardless ofinterrupted advancement of the specimen.

Referring to FIGS. 26 and 27 a top and side view of an embodiment of thetensioning device employed by the invention is shown. In this embodimentthe specimen exiting the reciprocating reducing dies 32 is partiallyinserted into the body of the grasping mechanism 138. Inside thegrasping mechanism a cam style clamping mechanism 142 is rotated by ahydraulic cylinder 140 to compress all or portion of the specimen inorder to prevent the exiting of the specimen. The grasping mechanism inthis embodiment is powered by carriage 150 sliding down a guide rail152. A motor 154 driving one or more pinion gears 156 along one or morerack gears 158 provides advancing force to the carriage 150. In thisembodiment a dampening mechanism such as the depicted air spring 148 canbe mounted between the grasping mechanism and the powering device toprovide a more continuous tensile load regardless of interruptedadvancement of the specimen.

Referring to FIG. 28 a cross-sectional view is shown of anotherembodiment of the die module which generates reciprocating motionthrough the powered eccentric shaft 44, in order to reduce theTee-shaped specimen 32. A connecting rod 46 couples the reciprocatingcarriage 48 with the eccentric shaft. In the preferred embodiment thecontact dies 36 are mounted directly to the reciprocating carriage. Justas in other embodiments the use of intermediary mounting structures forload distribution, heat flow management, or other functional reasons maybe desired and are congruent within the scope of the present invention.The reciprocating carriage is constrained constrains the reciprocatingmotion by a mounting pivoting shaft 160 coupled to the reciprocatingcarriage 48 with a swing arm 162. In this embodiment the reciprocationmotion 164 of the contacting dies 36 is not axial but a function ofangular rotation around the mounting pivot shaft 160 resulting in alevel of rotation component in the reciprocation. This rotationcomponent is not necessary for the operation of the reciprocation dieshowever small levels of rotation resulting from small reciprocationtravel driven by the eccentric and sufficiently long support arms isstill considered within embodiments of the invention. The mounting pivotshaft is mounted in a supporting frame 52 also in which the eccentricshaft is also mounted. Coupled with this reciprocating die motion atensioning device 30, provides axial advance and tension force 54, tothe Tee-shaped specimen 32.

The present invention is an improvement of the drawing process or adrawbench device with the use of an array of synchronized reciprocatingdies to input compressive work into the cross section of a shapedcomponent that is maintained in position under a desired tension.

The oscillating motion reducing the metal sections provides alleviationfor the tendency of the traditional drawing process to result in surfacedefects resulting from the workpiece being slid through static tapereddies. In the described innovation, deformation occurs as thesynchronized oscillating dies close in on one another while the specimenexperiences diminished axial advancement due to the tension beinginsufficient to advance the component through the die under compression.As the dies are allowed to retract on the other portion of thereciprocation cycle, the component is allowed to advance through thebite of the die under lower or absent contact pressure. This diminishedsliding during high contract pressure and advancement during lower orzero contact pressure minimizes surface sliding defects during drawing,particularly for galling sensitive materials and during drawing at hightemperatures. This invention reduces the requirement of highly effectivefriction reducing lubricants and allows processing of difficult tolubricate materials and utilization of processing temperatures above theavailability of effective drawing lubricants, enabling new productofferings.

The reduction of simple bar such as rounds, squares, rectangles, andtubes can be accomplished enveloping the periphery of the shape exteriorwith reciprocating dies as shown in FIG. 1 . A small gap would exist atthe locations where dies meet to allow independent motion. Tubes wouldrequire the use of static mandrel on the interior of the tube to yieldinternal surfaces.

The ability to reduce complex shaped components arises from thearrangement of reciprocating dies to form a series of spaces between thedies. The shape of these spaces can be influenced by profiling theworking surfaces of the dies and by changing their orientation relativeto one another. The resulting spaces will correspond with the desiredshaped component after gage reduction. The extremities of these spacesmay be open or partially closed to allow widening of component featuresor to discourage this widening effect.

The motion or direction of synchronized reciprocation should be suchthat the spaces between the die segments open and close in unison. Inthe preferred embodiment, the reduction imparted to material in eachindividual space between the die segments would receive equal strainfrom the draw pass to provide the least distortion or residual stress inthe drawn component. This is not requisite to the invention as theapplied axial tensile load provides a means of straightening and stressrelaxation through tensile stretching. The amount of reciprocation maybe smaller than the total reduction of the workpiece in the given pass,such that multiple reduction and advancement cycles are necessary for asegment to fully reduce and pass through the bite of the dies. In thisembodiment, only certain advancement of the workpiece will occur in agiven reciprocation cycle until the die opening motion stops and axialadvancement stops. This provides advancement speed regulation tied toreciprocation frequency, reciprocation stroke length, and die lead ingeometry. Other embodiments of this invention involve die strokes largerthan the total reduction of the workpiece in the given pass. In theseembodiments another device is present on the entry side of thereciprocating dies to provide a back tension against the pullingmechanism and to regulate the rate of axial advancement when the diescompletely disengage the workpiece.

Higher frequency reciprocation is generally preferred for productivityand die exposure reasons. However, frequency reciprocation must remainlow enough to allow axial advancement of the workpiece during theretraction phase of the reciprocation cycle. The invention may utilizeany suitable mechanism to power the reciprocation and providecompressive forces to the die. Many different methods for mounting andsupporting the various die segments can be utilized. As such, some levelof rotational motion and axial translation of the die segment during areciprocation cycle is considered permissible within the confines of theinvention but is not necessary for successful operation of theinvention.

In order to provide clearer illustration of the impact, novelty, andadvantages of the invention, the specifics of an application areprovided. This example is not to constrict the scope of the inventionand is to be considered in no way limiting.

Though many different materials are not conducive to working in the lowtemperature requirements seen in standard draw bench reduction, in thisspecific example precipitation hardening 17-4 PH illustrates this well.Imparting deformation too cold, or even too hot, results in the presenceof delta ferrite within the material and results in loss of transverseductility. This results in impractically brittle and anisotropic finalmaterial. In addition to ductility loss, delivery of desirable grainsize is influenced by the amount of deformation and the temperature atthe time of deformation, particularly in semi-austenitic grades. Toprevent this, a specific window of thermal processing must bemaintained, with a targeted temperature of 2150° F. for the case of 17-4PH stainless steel. The material, when properly hot worked, is desirablefor many uses due to considerably higher strengths than austeniticstainless steels or carbon steels which can be delivered in complexshaped structural members, available with prior art.

The aim geometry in this specific example is a Tee-shaped cross section,as illustrated in FIG. 2 , and is to be reduced to a finished size in asingle pass through the device. Also, the vertical portion of the crosssection is a different thickness than the horizontal base. The verticalsegment has a final reduced thickness of 0.100″ and a starting thicknessof 0.286″. The horizontal segment, for end application reasons, has athicker final reduced thickness of 0.200″ and a thicker startingthickness of 0.572″. This represents a 65% reduction in all segments ofthe cross section. This is approximately double the reduction typicallyachievable with standard draw bench techniques, while achieving similaror faster draw velocities. The delivery of finished segment with onepass has a significant improvement on throughput and processing costsfor drawn product. The entry sides of the dies flare outward to create acontact face during the reduction process. Though not always the case,in this example the entry geometry is of constant angle slopes. Theentry geometry for die segments contacting the vertical feature of the Tshape will have a slope of 7.1° while the die entry for the horizontalsegment will have a slope of 14°. In this example the length of segmentbeing reduced, or “transition zone” here forth referred, is 0.75″ longfor both vertical and horizontal segments. A short segment of die, 0.5″long, imparting minimal or no reduction is present to “trowel” or smooththe surface of the drawn Tee.

The dies surrounding this Tee shape will open and close, in synchronous,to impart the reduction into the specimen as it passes through the dies.The two dies adjacent the vertical segment of the Tee-section have bothvertical and horizontal motion components as they move upward and off ofthe horizontal segment and outward and off of the vertical segment. Thelower die only has a vertical motion component. The horizontal componentof travel of the upper dies is 0.010″ in and out for each side(providing a 0.020″ total gap reciprocation). The vertical component oftravel of the upper dies and the only component of travel of the lowerdie are both 0.021″ per side (providing a 0.042″ total gapreciprocation). Combining the X and Y component for the upper diesresults in a reciprocation of 0.023″ of travel in a direction of 63°angle from horizontal. With each opening motion of reciprocation of thedies, the tensioning specimen advances the Tee segment 0.083″ forwardprior to re-engagement of the contact faces. As a result, the specimenis reduced by several die reciprocations as it passes between the diesand is fully reduced to the target thickness. A portion of the reductionmanifests as a widening of the cross-sectional features on the Teesegment and should be offset by inputting a slightly narrower inputstock. However, the majority of the thickness reduction manifests in theform of elongation. In this example, the typical exit velocity ratio of2.6 to 1. This however can vary with parameters such as contactfriction, entry geometry, and die temperatures. With a reciprocationfrequency of 1800 reciprocations per minute (30 Hz) coupled with anentry advance of 0.083″ the resulting entry speed of 12.5 ft/minute isgenerated. Due to the elongation from reduction, an exit velocity of31.25 ft./minute is generated. The resulting processing speed wouldyield 20 ft of usable finished length in 38 seconds. Reciprocatingfrequencies of about 8-3600 rpms and entry speeds of about lft/min to150 ft/min may be utilized accordingly to the invention.

During this reduction the exit material is maintained under tension bypulling against the reducing die segments. Though die reciprocationresults in brief release of the segment, tension is reestablished withcontact with die following incremental advancement. The magnitude oftensile force is such as to provide nearly instantaneous advancement ofthe segment each time the dies open as well as to impart a slightyielding in the axial direction. Given that reduction amounts are somuch higher than those in tradition draw bench design, there is noconcern that applied tension would advance the segment in the bite ofthe dies in an unintended way through sliding. This disconnect oftension from the reduction amount allows the magnitude to be adjusted tobe high enough to straighten the segments but low enough not to neck thecomponent and compromise dimensional integrity of the section. Thisability to adjust tension independently of the reduction amount isunique to the process and historically has been merely a product of thereduction amount in traditional draw bench applications. This ability todeliver robust straightness in the same operation eliminates the cost ofeither additional draw operations for the purpose of straightening orseparate straightening operations with separate equipment, thus furtherimproving the cost structure of drawn components.

This invention's introduction of synchronized reciprocation of diesegments to reduce a workpiece on a draw bench allows for performanceimprovement compared to prior art. In all prior art in draw benchapplications the tension force on exiting material was set by the forcerequired to pull the workpiece through a die and impart the reduction ofthat pass. Limits on reduction strain magnitude arose when the desiredreduction strain would require an axial tensile force in excess of whatthe exiting cross section could support without excessive stretching,deformation, or tearing. In the present invention, the axial tensileload is no longer dictated by the reduction amount, since reduction islargely accomplished by the reciprocating die segments. Reductions muchhigher than prior art can be achieved with lower axial tensile forces.Simultaneously with much higher reduction strains, the axial tensileforce can be adjusted to yield optimum straightness and residual stresslevels without significant influence to drawing productivity, providedaxial tensile forces are sufficient to adequately advance the workpieceduring the retraction phase of the reciprocation cycle and not in excessof axial forces required to slide the piece forward in the bite duringthe compressive phase of the reciprocation cycle.

A provision for tensioning outgoing material in a traditional draw benchis commonly delivered using a clamping device on a traveling carriage.In this invention the presence of a tensile load of a desired magnitudeis the only requirement and is independent of which suitable mechanismis chosen to deliver this tensile load. All suitable mechanisms fordelivering tensile load on material exiting after the reduction processare considered embodiments of this core invention.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations may be made herein without departing from the spirit andscope of the invention as defined by the appended claims.

Certain terms are used throughout the description and claims to refer toparticular features or components. As one skilled in the art willappreciate, different persons may refer to the same feature or componentby different names. This document does not intend to distinguish betweencomponents or features that differ in name but not structure orfunction. For example, as used herein “reciprocating die,” “diesegment,” “reciprocating contact die,” “reciprocating die module,” “diemodule,” and similar terms are interchangeable and refer to the diesegments cited in the claims. Likewise, “specimen,” “metal segment,”“work piece,” and similar terms are interchangeable and refer to thespecimen cited in the claims.

What is claimed is:
 1. A method of shaping a specimen comprising; a)providing at least one pair of reciprocating dies, b) advancing thespecimen under tension through a space between the reciprocating dies,and c) impacting at least two surfaces of the specimen with thereciprocating dies to shape the specimen.
 2. The method of claim 1wherein the dies travel a distance less than an amount of a reduction insize of the specimen in a given pass through the dies.
 3. The method ofclaim 1 wherein the dies travel a distance greater than an amount of areduction in size of the specimen in a given pass through the dies andfurther including the step of grasping the segment on an entry side ofthe reciprocation dies whereby tension is maintained.
 4. The method ofclaim 1 wherein the dies have a contact surface comprising two or moresurfaces that intersect each other.
 5. The method of claim 1 wherein thecycle time of the reciprocating dies and the travel speed of thespecimen is selected based upon the material of the metal segment. 6.The method of claim 1 wherein the final shape of the specimen isdetermined by the configuration of the contact surfaces of the dies andgaps between the dies.
 7. A method for cross sectional reducing andstraightening a specimen comprising: advancing a specimen under tensionthrough a plurality of die segments; wherein each die segment has acontact face; at least one of the die segments wherein the contact facehas at least two planar surfaces that intersect to form a convexfeature; the plurality of die segments configured such that the contactface of each die segment is opposed by the contact face of at least oneother die segment to form at least one set of opposing die segments; theplurality of die segments configured such that the geometry of theplurality of die segments is not restricted to converge on a radialcenter; at least one die gap determined by the distance between thecontact faces of the at least one set of opposing die segments; at leastone die driving mechanism providing translational motion to at least onedie segment, the translation motion being directed toward the opposingdie segment; the die driving mechanism configured to providereciprocating translational motion to at least one die segment andsynchronous reciprocating motion to the plurality of die segments,whereby the at least one die gap opens and closes; and, wherein thetension is provided by an exit tensioning device configured to grip aspecimen and maintain a continuous tension on the specimen causing thespecimen to move with a translational motion through the at least onedie gap and cross sectionally reducing the specimen by a predeterminedreduction, the reciprocating transitional motion of the opposing diesegments being less than the predetermined reduction, the continuoustension being insufficient to provide the translational motion to thespecimen during the compression phase; whereby the specimen will bereduced, stretch straightened, elongated, and have enhanced mechanicalproperties.
 8. A method for cross sectional reducing and straightening aspecimen comprising: advancing a specimen under tension through aplurality of die segments; wherein each die segment has a contact face;at least one of the die segments wherein the contact face has at leasttwo planar surfaces that intersect to form a convex feature; theplurality of die segments configured such that the contact face of eachdie segment is opposed by the contact face of at least one other diesegment to form at least one set of opposing die segments; the pluralityof die segments configured such that the geometry of the plurality ofdie segments is not restricted to converge on a radial center; at leastone die gap determined by the distance between the contact faces of theat least one set of opposing die segments; at least one die drivingmechanism providing translational motion to at least one die segment,the translation motion being directed toward the opposing die segment;the die driving mechanism configured to provide reciprocatingtranslational motion to at least one die segment and synchronousreciprocating motion to the plurality of die segments, whereby the atleast one die gap opens and closes; wherein the tension is provided byan exit tensioning device and an entry back tensioning device; whereinthe exit tensioning device is configured to grip a specimen and theentry back tensioning device is configured to grip the specimen oppositeto the exit tensioning device, the exit tensioning device and the entryback tensioning device further configured to maintain constant tensionon the specimen, cause the specimen to move with a translational motionthrough the at least one die gap, and cross sectionally reduce thespecimen by a predetermined reduction, the reciprocating translationalmotion of the opposing die segments being less than or greater than thepredetermined reduction, and the tension being insufficient to providethe translational motion to the specimen during the compression phase;whereby the specimen will be reduced, stretch straightened, elongated,and have enhanced mechanical properties.